It has previously been proposed to provide detectors for electromagnetic energy, and particularly millimeter wave and infrared radiation that exploit the temperature-sensitive properties of ferroelectric devices. For example, U.S. Pat. No. 4,902,895 discloses a system wherein a ferroelectric material is placed between two electrodes or plates to form a capacitor and the charge accumulated in the capacitor during exposure to radiation is read out to measure the radiation. In U.S. Pat. No. 5,530,247 similar elements are incorporated into a two-dimensional array so that the charge build-up in the ferroelectric layers during exposure to radiation may be converted to a readable image and displayed by video screen. U.S. Pat. No. 6,534,767 includes a ferroelectric element connected in a resonant circuit. The resonant frequency of the circuit, which varies with the radiation incident on the ferroelectric element, is tracked by a phase-locked loop.
These systems are inherently expensive and relatively slow in operation. Independently, technologies for measuring frequency have advanced so significantly in recent years that systems based on frequency measurements have become highly precise, very fast in operation, and relatively low in cost.